Effect of current pulse width on xenon Z-pinch discharge plasma for extreme ultraviolet source

Abstract

Extreme ultraviolet (EUV) lithography is the leading candidate as the next-generation technique for printing semiconductor chips at the half-pitch 22 nm node and even beyond. The source of EUV radiation remains a key issue for industrial application of EUVL. Previously, our group has designed both xenon and tin plasma as EUV source. Studies on EUV emission and plasma dynamics indicated that Z-pinch plasma motion along the axial direction may enlarge the size of EUV-emitting plasma, un-favorable for its application as the EUVL source due to the limit of EUV scanner. Amplitude, rise time and duration of the current pulse, affecting the plasma dynamics and EUV-emitting size are most important parameters. In this paper, we present a study of current pulse effects on the xenon plasma EUV source. The shortest current pulse width has been reduced to 85 ns by decreasing the inductance of discharge circuit. Four current pulse conditions have been designed with current pulse widths of 85 ns, 110 ns, 230 ns and 460 ns. Here, comparative results of the 85 ns and 110 ns current-driven xenon Z-pinch plasma EUV sources are reported, and EUV signals, EUV-emitting plasma size and plasma dynamic motion are compared. Results show that use of a shorter current pulse inhibits the axial plasma outflow, and both axial and radial size of EUV-emitting plasma have been reduced, which benefits its application as EUV lithography source.